Charge dependence of electron emission in swift heavy-ion collisions with carbon

Abstract

We report on the charge dependence of electron yields from sputter-cleaned amorphous carbon targets bombarded with an isotachic set of swift ions. The experiments were performed in a UHV setup at the heavy-ion accelerator GANIL in Caen. The ion velocity was 19 a.u. (corresponding to a kinetic energy of 9.2 MeV/nucleon) and the projectile charge QP was varied from 6 to 39. As observed for ion-atom collisions, the electron yield exhibits a reduction with respect to a Q2P law. We show that this projectile charge dependence is consistent with a strong saturation of low-energy primary electron ejection. This effect is related to the primary projectile-target interaction itself and not to high-charge effects affecting the electron transport before escape from the target.